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Impact of Acrylic Vessel Thickness

Impact of Acrylic Vessel Thickness. Liang Zhan. AV variation. Baseline: AD of G4dyb release2_4. ESR radius of 2.3m, 5cm away from outer AV endcaps. No ribs and calibration pipes. Vary inner AV thickness and the change is compensated by LS thickness variation.

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Impact of Acrylic Vessel Thickness

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  1. Impact of Acrylic Vessel Thickness Liang Zhan Liang Zhan

  2. AV variation • Baseline: AD of G4dyb release2_4. • ESR radius of 2.3m, 5cm away from outer AV endcaps. • No ribs and calibration pipes. • Vary inner AV thickness and the change is compensated by LS thickness variation. 10mm, 15mm, 20mm, 25mm, 30mm. Liang Zhan

  3. Simulation method • Three impacts • Neutron detection efficiency • Positron detection efficiency • Spectrum variation • Three types of event are simulated • Neutron event (InverseBeta generator) • No optical photon • Generated inside of gamma catcher. • Gamma event • To find the 1MeV energy cut. • Generated in GdLS target • Neutrino event (InverseBeta generator) • With optical photon simulation. • Positron + neutron, generated inside of gamma catcher Liang Zhan

  4. Neutron events • A million events for each AV thickness. • Without optical photon, 6MeV E deposit cut is applied. • Efficiency = (E deposit > 6MeV )/Gd capture events Liang Zhan

  5. Neutron efficiency • Typical efficiency uncertainty at 10mm thickness • Suppose energy scale variation: 6MeV+/-0.6MeV Then efficiency variation: 90.9+/-0.25% • Stat. error ~ 0.05%. Liang Zhan

  6. Gamma event • To find the 1MeV energy cut in the positron PE spectrum. • 1MeV  113PE for 10mm AV thickness Thickness = 10mm Liang Zhan

  7. Positron efficiency • Efficiency = (PE > PE cut) / neutron signal passing 6MeV cut. • 50000 neutrino events are simulated, not adequate. Liang Zhan

  8. A possible solution to increase the stat. quality is • Suppose the efficiency of >2MeV positron is 1.0. • Then simulate the <2MeV positron and calculate the Inefficiency. • Calculate the Ratio of <2MeV positron in generated positrons by InverseBeta generator. • The inefficiency should be Inefficiency(<2MeV)/Ratio Liang Zhan

  9. Neutron efficiency by PE cut • Efficiency = (PE > 6MeV PE cut) / Gd capture events • 50000 events, about 22000 are captured by Gd. Liang Zhan

  10. Conclusion • Neutron efficiency decreases about 2% if 10mm changes to 25mm by with/without optical photon simulation. • A million neutron events show uncertainty of neutron efficiency changes from 2.5% to 3.2% (10mm25mm) • The discrepancy of neutron efficiency between with and without optical photon simulation is due to the energy calibration. • The stat. error of positron efficiency is too big compared to the uncertainty. Liang Zhan

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